The present invention relates to a laser beam machining apparatus in which work pieces, such as iron plates, are placed on machining pallets and each of the work pieces is moved from a setting position to a laser machining position so that the work pieces are machined. More particularly, the present invention relates to a laser beam machining apparatus which is capable of omitting a unit for vertically moving pallets from a pallet storage unit to thereby improve the working efficiency with a simple structure.
In Japanese Patent Unexamined Publication No. Hei. 6-15475, disclosed is a carriage unit adaptable to a laser beam machining apparatus of the foregoing type and attempted to improve the rate of operation of the laser beam machining apparatus by employing a structure that a plurality of pallets are stacked in a vertical direction (i.e. upper and lower direction) and accommodated in a pallet storage unit and the pallets are exchanged whenever a machining operation is completed.
However, the above-mentioned carriage unit suffers from a problem in that a large space is required to install the pallet storage unit and large facilities relating to the laser beam machining apparatus must be provided.
Moreover, flat work pieces and stereoscopic work pieces each having a height larger than that of the flat work piece cannot mixedly be accommodated in corresponding pallets.
On the other hand, the Japanese Patent Unexamined Publication No. Sho. 63-16895 teaches a technique relating to the carriage unit in which only two pallet storage units are provided to reduce the required space and to minimize the facilities for handling pallets.
The above-mentioned carriage unit has a structure that two pallet-accommodating portions are vertically arranged for a pallet storage unit to accommodate pallets for only the upper portion and those for only the lower portion in the upper and lower pallet accommodating portions. To make the height at which the machine performs the operation to be constant, a unit for vertically moving the pallets is provided for the pallet storage unit. Thus, a work piece is placed on the lower pallet to wait for start of a next machining operation during a process in which the material on the upper pallet is being machined.
After the operation for machining the work piece on the upper pallet has been completed, the upper pallet is accommodated in the upper portion of the pallet storage unit, and then the pallet storage unit is moved upwards by the carriage unit to carry the lower pallet to the machine. During the process for machining the work piece on the lower pallet, a machined product in the upper portion of the pallet storage unit is extracted to be changed for a new work piece.
When the operation for machining the lower work piece has been completed, the pallet is returned to the lower pallet storage unit. Then, the pallet storage unit is moved downwards by the unit for vertically moving the pallet storage unit to move the upper pallet to the machine. The above-mentioned vertical movements are repeated so that the operation for machining work pieces with laser beams is performed.
The conventional carriage unit for the laser beam machining apparatus must be provided with an elevating unit for the pallet storage unit to make the heights of the plurality of the moving pallets to be constant. Thus, there arises a problem in that the structure becomes too complicated. Moreover, the pallet storage units respectively arranged for only the upper portion and the lower portion require the operation for vertically moving the pallets whenever the machining operation is completed. Thus, a long time is required and thus a problem arises in that a waiting time is elongated excessively during the machining operation which is performed by the laser beam machining apparatus.